JP7287365B2 - Air pressure control device, air pressure control method, and air pressure control program - Google Patents

Description

The present invention relates to an air pressure management device, an air pressure management method, and an air pressure management program for managing tire air pressure.

Driving stability of the vehicle is ensured by properly inflating a plurality of tires mounted on the vehicle. Tire pressures of this type generally degrade over time due to natural leakage. Since the absolute value of the air pressure reduction amount depends on the air pressure of the tire, for example, in the case of tires for trucks and buses, the air pressure may decrease by about 30 to 50 (kPa) in one month. In addition to the natural leakage described above, it is assumed that the tire pressure will drop rapidly due to problems such as punctures, valve failures, and wheel damage. For this reason, conventionally, the degree of tire air pressure decrease that indicates the tendency of tire air pressure to decrease is calculated, and based on this degree of tire air pressure decrease, the time required for the air pressure to decrease to the set air pressure is estimated. A technique has been proposed for notifying the driver of the decrease time (see, for example, Patent Literature 1).

JP 2006-327554 A

By the way, the degree of decrease in tire air pressure, which indicates the tendency of tire air pressure to decrease, varies greatly depending on the specifications of the tire, the environment in which it is used (temperature), and the air pressure filled in the tire. For this reason, when determining whether or not there is an abnormality by comparing the degree of decrease in tire air pressure with a threshold value, there is a problem that it is difficult to accurately determine with a constant threshold value.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an air pressure management device, an air pressure management method, and an air pressure management program capable of accurately determining whether or not there is an abnormality in tire air pressure.

In order to solve the above-described problems and achieve the object, an air pressure management device according to the present invention includes a temperature-converted air pressure calculation unit for calculating a temperature-converted air pressure of a tire based on acquired tire temperature and air pressure, and a predetermined temperature-converted air pressure. An air pressure drop rate calculation unit that calculates an air pressure drop rate indicating a decrease trend of tire air pressure from the amount of change in temperature-converted air pressure over a period of time, and a threshold table defining air pressure drop rate thresholds associated with predetermined physical quantities related to tires. Using an air pressure decrease speed threshold setting unit that sets an air pressure decrease speed threshold corresponding to the acquired physical quantity, and based on the calculated air pressure decrease speed and the set air pressure decrease speed threshold, whether the tire air pressure is abnormal and a first determination unit that determines whether or not.

In the air pressure management device described above, the physical quantity is preferably any one of the thermal history amount, temperature, and air pressure of the tire.

Further, in the air pressure management device described above, the air pressure decrease speed calculation unit calculates the air pressure decrease speed of each paired pair of tires based on the wheel positions of the vehicle on which the tires are mounted, and calculates the deviation of each air pressure decrease speed. It is preferable to provide a second determination unit that determines whether or not the air pressure of one of the pair of tires is abnormal based on the above.

Further, the air pressure management device described above preferably includes a table update unit that acquires the physical quantity and the air pressure drop speed of the tire and updates the threshold table based on the acquired physical quantity and air pressure drop speed.

Further, in the air pressure management device described above, it is preferable that the table updating section acquires the physical quantity and the air pressure decrease rate of the tire having the same specifications as the tire accumulated in the external device.

Further, in the air pressure management device described above, when the first determination unit determines that the tire air pressure is abnormal, the tire air pressure decreases to the limit air pressure when the tire is continuously used at the calculated air pressure decrease rate. It is preferable to provide a notification unit that notifies the time until the time.

Further, the air pressure management method according to the present invention includes the steps of calculating the temperature-converted air pressure of the tire based on the acquired tire temperature and air pressure, and the steps of calculating the air pressure decrease speed from the amount of change in the temperature-converted air pressure in a predetermined period. setting an air pressure decrease speed threshold value corresponding to the obtained physical quantity using a threshold table that defines an air pressure decrease speed threshold value associated with a predetermined physical quantity related to the tire; determining whether the air pressure of the tire is abnormal based on the pneumatic pressure drop rate threshold.

Further, the air pressure management program according to the present invention includes the steps of calculating the temperature-converted air pressure of the tire based on the obtained tire temperature and air pressure, and the steps of calculating the air pressure decrease speed from the amount of change in the temperature-converted air pressure in a predetermined period. setting an air pressure decrease speed threshold value corresponding to the obtained physical quantity using a threshold table that defines an air pressure decrease speed threshold value associated with a predetermined physical quantity related to the tire; determining whether or not the air pressure of the tire is abnormal based on the air pressure decrease speed threshold.

According to the present invention, whether or not the tire air pressure drop is abnormal is determined based on the air pressure drop speed threshold and the air pressure drop speed set corresponding to the current physical quantity. The presence or absence of an abnormality can be determined with high accuracy.

FIG. 1 is a schematic diagram showing a vehicle equipped with an air pressure management device according to this embodiment. FIG. 2 is a block diagram showing functional configurations of an air pressure management device and a server device. FIG. 3 is a flow chart showing the operation procedure of the air pressure management device. FIG. 4 is a diagram showing the relationship between the temperature detected in a predetermined period and the detection frequency. FIG. 5 is a diagram showing the relationship between the temperature acceleration factor and temperature. FIG. 6 is a schematic diagram of a threshold table showing the relationship between the amount of thermal history and the air pressure drop degree threshold. FIG. 7 is a diagram showing an estimated air pressure drop time until the air pressure reaches the limit air pressure. FIG. 8 is a diagram for explaining the operation of generating a threshold table based on information on the amount of thermal history and the rate of air pressure decrease. FIG. 9 is a schematic diagram of a threshold table showing the relationship between air pressure and air pressure drop threshold.

EMBODIMENT OF THE INVENTION Below, embodiment of the air pressure management apparatus which concerns on this invention is described based on drawing. It should be noted that the present invention is not limited by this embodiment. In addition, components in the present embodiment include those that can be replaced by those skilled in the art and can be easily conceived, or substantially the same components.

FIG. 1 is a schematic diagram showing a vehicle equipped with an air pressure management device according to this embodiment. FIG. 2 is a block diagram showing functional configurations of an air pressure management device and a server device. An air pressure management device 10 according to this embodiment is arranged in a vehicle 1 and manages the air pressures of a plurality of tires 2 of the vehicle 1 . Specifically, the air pressure management device 10 monitors the air pressure decrease speed of each tire 2 as air pressure management, and when the air pressure decrease speed exceeds a threshold value, the air pressure of the tire 2 is abnormal. and report.

As shown in FIG. 1 , a plurality of tires 2 of a vehicle 1 are provided with sensors 3 respectively, and these sensors 3 are communicably connected to an air pressure management device 10 . The vehicle 1 is also provided with an outside air temperature sensor 4 that measures the outside air temperature. The outside air temperature sensor 4 is provided at a location that is not easily affected by disturbances such as direct sunlight and engine waste heat, and is connected to the air pressure management device 10 so as to be communicable. Moreover, the vehicle 1 in which the air pressure management device 10 is arranged is preferably a truck or a bus that has relatively large tires 2 and runs a long distance, but it is not limited to this.

The sensor 3 is a TPMS (Tire Pressure Monitoring System) sensor, and includes an air pressure sensor 3a that measures the air pressure of the tire 2 and a temperature sensor 3b that measures the temperature of the air inside the tire 2 . Moreover, the sensor 3 may be configured to further include an acceleration sensor that measures centrifugal acceleration acting on the tire 2 . A sensor 3 is attached, for example, to the air valve of each tire 2 . A sensor ID (identification information) is set for each sensor 3, and the sensor ID of the sensor 3, the tire ID (identification information) of the tire 2 provided with the sensor 3, and the wheel position on which the tire 2 is mounted. (For example, in trucks and buses, the corresponding relationship with the left front wheel, right front wheel, left inner rear wheel, left outer rear wheel, right inner rear wheel, or right outer rear wheel) is registered in the air pressure management device 10 . The measurement data of each sensor 3 can be transmitted to the air pressure management device 10 at predetermined time intervals, for example, using short-range wireless communication such as RF (radio frequency) communication. In the present embodiment, air is exemplified as the gas to be filled in the tire 2, but this air includes air adjusted to have a nitrogen ratio higher than usual (for example, 98% or more).

The air pressure management device 10 is an in-vehicle device mounted on the vehicle body of the vehicle 1 . As shown in FIG. 2, the air pressure management device 10 includes a sensor receiver 11, a storage unit 12, a communication unit 13, a display unit (notification unit) 14, a route guide unit 15, a control unit 16, a temperature converted air pressure calculation unit 17, It has an air pressure decrease speed calculation unit 18 , a thermal history amount calculation unit (physical quantity acquisition unit) 19 , an air pressure decrease speed threshold value setting unit 20 , a table update unit 21 , a first determination unit 22 and a second determination unit 23 . In addition, the air pressure management device 10 is communicably connected to a predetermined server device (external device) 30 via a communication network 40 such as an Internet line. In the present embodiment, the air pressure management device 10 will be described as an in-vehicle device mounted in the vehicle 1, but it is not limited to this. may be connected to the vehicle 1 by

The sensor receiver 11 receives (obtains) data transmitted from each of the sensors 3 (the air pressure sensor 3 a and the temperature sensor 3 b ) of the plurality of tires 2 and the outside air temperature sensor 4 . In the present embodiment, the air pressure management device 10 is integrally provided with the sensor receiver 11, but the sensor receiver 11 may be separately mounted on the vehicle.

The storage unit 12 is configured by including storage means such as a volatile or nonvolatile memory or HDD. The storage unit 12 stores various programs executed by the control unit 16 and various data. In this embodiment, the storage unit 12 stores information on the air pressure and temperature of each tire 2 and information on the outside air temperature received by the sensor receiving unit 11 at predetermined time intervals. In this case, it is preferable to determine the corresponding tire ID and wheel position from the sensor ID and store the information of the air pressure and temperature of each tire 2 as history information in which they are associated with each other. Further, when the tire 2 is rotated in the vehicle 1, the correspondence relationship between the tire ID (sensor ID) registered in the air pressure management device 10 and the wheel position is corrected.

The communication unit 13 is configured to be wirelessly communicable with the server device 30 as an external device via the communication network 40 . In this embodiment, the communication unit 13 periodically transmits to the server device 30 the amount of heat history (physical quantity) received by the tire 2 of the own vehicle and the air pressure decrease rate of the tire 2 . The amount of thermal history and the air pressure decrease rate of the tire 2 can be calculated from the air pressure and temperature of the tire 2, respectively. A database is formed in the server device 30 for each tire specification (model number, size, etc.). stored in the database. In this case, the communication unit 13 may acquire, from the database of the server device 30 under the control of the control unit 16, information on the amount of heat history and the rate of decrease in air pressure of tires having the same specifications as the tires 2 of the own vehicle. .

The display unit 14 is a display device that is arranged on a dashboard of the vehicle body or the like, and has a display screen that displays various types of information and provides the user (driver) with the display screen. In this embodiment, for example, map information including a route to a set destination, and information on the current air pressure, temperature, and outside air temperature of each tire 2 mounted on the vehicle 1 are displayed. The display unit 14 can also display information about the temperature-converted air pressure calculated based on the air pressure and the temperature and the air pressure decrease rate. Further, the display unit 14 displays the determination result of whether or not the air pressure of the tire 2 is abnormal based on the air pressure decrease rate, and if the air pressure is determined to be abnormal, the tire 2 is mounted. Information about the period (distance) during which the vehicle 1 can travel can be displayed. Therefore, in this embodiment, the display unit 14 functions as a notification unit that notifies that the air pressure of the tire 2 is abnormal.

The route guidance unit 15 has a so-called navigation function, searches for a route from the current location of the vehicle 1 to a destination, and provides route guidance. For example, when it is determined that the air pressure of the tire 2 is abnormal, the route guidance unit 15 searches for a route from the current position of the vehicle 1 to the nearest maintenance service shop and provides route guidance.

The control unit 16 includes a CPU (Central Processing Unit), a ROM (Read-Only Memory), a RAM (Random-Access Memory), and the like. controls the behavior of For example, if the air pressure of the tire 2 is determined to be abnormal, the time required for the air pressure of the tire 2 to decrease to the limit air pressure (pneumatic pressure decrease Estimated time) is estimated, and this estimated air pressure decrease time is displayed on the display unit 14 .

Under the control of the control unit 16, the temperature-converted air pressure calculation unit 17 calculates a temperature-converted air pressure by converting the air pressure at a predetermined temperature based on the acquired temperature and air pressure of each tire 2. FIG. In general, the air pressure of the tire 2 tends to change according to the air temperature. Therefore, the air pressure may differ between when the vehicle is running and when the vehicle is stopped, making it difficult to accurately manage the air pressure fluctuations. Therefore, the temperature-converted air pressure calculator 17 converts the air pressure of the tire 2 into air pressure at a specified temperature (for example, 25° C.) based on, for example, Boyle-Charles' law. According to this, fluctuations in the air pressure associated with changes in the temperature of the tire 2 are suppressed, and changes in the air pressure can be managed accurately.

Under the control of the control unit 16, the air pressure decrease speed calculation unit 18 calculates the air pressure decrease speed from the amount of change in the temperature-converted air pressure during a predetermined period. The air pressure drop rate is a value that indicates the tendency of air pressure to drop based on the amount of air pressure drop (kPa) per unit time (for example, 1 minute). In general, the air pressure of tires decreases over time due to natural leakage. Since the absolute value of this air pressure drop depends on the air pressure of the tire, for example, in the case of tires for trucks and buses, the air pressure may drop by 30 to 50 (kPa) in one month. On the other hand, in the case of troubles such as tire puncture, valve failure, and wheel damage, the rate of decrease in air pressure is significantly greater than in the case of natural leakage. Therefore, by paying attention to this pneumatic pressure decrease rate, it is possible to detect tire troubles at an early stage. It is preferable that the air pressure decrease speed calculator 18 repeatedly calculate the air pressure decrease speed from the amount of change in the temperature-converted air pressure for a predetermined period (for example, 5 minutes). According to this, it is possible to accurately and early determine whether the air pressure of the tire is abnormal.

Under the control of the control unit 16 , the thermal history calculation unit 19 periodically or in real time calculates the amount of heat history received by the tire 2 for a predetermined period based on the obtained temperature information of each tire 2 . The thermal history amount is also called TSN (Temperature Severity Number), and is an index indicating the amount of heat received by the tire 2 in a predetermined period. indicates that This is because when the temperature of the tire 2 increases, the air permeability coefficient of the rubber member forming the tire 2 also increases. In addition, the temperature of the tire 2 largely fluctuates depending on the heat generation of the tire itself when the vehicle 1 is running and the outside air temperature when the vehicle 1 is running. It is preferable that the predetermined period is set to at least one day or longer.

The air pressure decrease speed threshold setting unit 20 sets an air pressure decrease speed threshold under the control of the control unit 16 . The air pressure decrease speed threshold is a threshold for determining whether or not the air pressure of the tire 2 is abnormal in comparison with the air pressure decrease speed described above. Therefore, the air pressure decrease rate threshold is defined by the air pressure decrease amount (kPa) per unit time (for example, 1 minute), like the air pressure decrease rate. In this type of determination, it is possible to set the air pressure decrease speed threshold to a fixed value. It becomes difficult to accurately determine whether there is an air pressure abnormality.

Therefore, the air pressure decrease rate threshold is set in association with the amount of thermal history, which is a predetermined physical quantity related to the tire 2, and varies according to the amount of thermal history. In this embodiment, the air pressure decrease speed threshold setting unit 20 includes a threshold table 20a that defines air pressure decrease speed thresholds associated with thermal history amounts. An air pressure drop rate threshold corresponding to the amount of thermal history is set. According to this configuration, it is possible to change the air pressure decrease speed threshold to be set according to the amount of heat history, so that it is possible to accurately determine whether or not there is an abnormality in the air pressure of the tire 2 .

Further, the correspondence relationship between the air pressure decrease rate threshold value and the amount of thermal history can be set by, for example, an actual machine test using tires 2 of the same specification, a simulation, or the like. In the present embodiment, the air pressure decrease speed threshold setting unit 20 is configured to include the threshold table 20a that defines the air pressure decrease speed threshold associated with the amount of heat history. 12 may be provided.

Under the control of the control unit 16, the table updating unit 21 updates the threshold table 20a of the air pressure decreasing speed threshold setting unit 20 periodically or at a predetermined timing based on the acquired information regarding the amount of heat history and the air pressure decreasing speed. In this embodiment, the table updating unit 21 acquires information about the amount of heat history and the rate of decrease in air pressure of tires having the same specifications (model number and size) as the tires 2 of the own vehicle from the database of the server device 30 . The table updating unit 21 obtains an approximate expression representing the relationship between the amount of thermal history and the air pressure decrease rate from the acquired plurality of information, and adds a predetermined margin to this approximate expression to determine the relationship between the amount of heat history and the air pressure decrease rate threshold. , and updates the threshold table 20a to the new threshold table 20a. This predetermined margin is set, for example, to a constant value and determined by experiments and empirical rules.

According to this configuration, the threshold table 20a is updated based on the information about the amount of heat history and the rate of decrease in air pressure acquired from the database. It is possible to notify the driver of the air pressure abnormality at an early stage. In the present embodiment, the table updating unit 21 acquires information about the amount of heat history and the rate of decrease in air pressure from the database of the server device 30. However, the present invention is not limited to this. Information about the amount of heat history and the air pressure decrease rate of the tire 2 accumulated in the vehicle may be acquired, and the threshold table 20a may be updated based on the information about the amount of heat history and the air pressure decrease rate.

The first determination section 22 determines whether or not the air pressure of the tire 2 is abnormal under the control of the control section 16 . Specifically, the first determination unit 22 compares the air pressure decrease speed calculated by the air pressure decrease speed calculation unit 18 with the air pressure decrease speed threshold set by the air pressure decrease speed threshold setting unit 20, thereby determining whether the tire 2 Determine whether the air pressure is abnormal. The first determination unit 22 determines that the air pressure of the tire 2 is abnormal when the air pressure decrease speed is greater than the air pressure decrease speed threshold, and when the air pressure decrease speed is equal to or less than the air pressure decrease speed threshold, the tire 2 air pressure is normal.

Under the control of the control unit 16, the second determination unit 23 determines whether or not there is an abnormality in the air pressure of a pair of tires 2 paired in advance. First, the air pressure decrease speed calculator 18 calculates the air pressure decrease speed of a pair of tires 2 paired in advance based on the wheel positions of the vehicle 1 . Normally, the temperature of the tire 2 tends to be higher at the inner wheel position of the vehicle 1 than at the outer wheel position, and the air pressure tends to decrease. For this reason, the pairing is set at opposing positions where the temperatures of the tires 2 are approximately the same (for example, the left front wheel and the right front wheel, the left inner rear wheel and the right inner rear wheel, the left outer rear wheel and the right outer rear wheel). ing. The second determination unit 23 determines whether or not the air pressures of the pair of tires described above are abnormal based on the calculated deviation of each air pressure decrease rate. In the present embodiment, the tires are paired at positions where the temperatures of the tires 2 are approximately the same. Therefore, the calculated pneumatic pressure decrease speeds are also approximately the same, and the deviation is considered to be close to zero. However, if one tire 2 has a problem and the air pressure decrease rate increases, the deviation of each air pressure decrease rate becomes larger than a predetermined threshold, so that the air pressure abnormality of the tire 2 can be determined. As described above, in this configuration, based on the deviation of the air pressure decrease rate of the paired pair of tires 2, in order to determine whether there is an abnormality in the air pressure of one tire 2 of the pair of tires 2, For example, it is possible to accurately determine whether or not there is an abnormality in the air pressure of the tire 2 even in the initial stage of occurrence of a problem. Therefore, by combining the determination by the second determination unit 23 with the determination by the first determination unit 22, it is possible to accurately and quickly determine whether the air pressure of the tire 2 is abnormal.

On the other hand, server device 30 is communicatively connected to air pressure management device 10 , holds information transmitted from air pressure management device 10 , and transmits necessary information in response to a request from air pressure management device 10 . The server device 30 includes a communication section 31, a storage section 32, and a control section 33, as shown in FIG.

Communication unit 31 is configured to be able to wirelessly communicate with air pressure management device 10 via communication network 40 . The communication unit 31 receives information about the amount of thermal history and the rate of decrease in air pressure of the tires of the own vehicle, which are transmitted from each air pressure management device 10 . Further, in response to a request from the air pressure management device 10 , the communication unit 31 transmits to the air pressure management device 10 information about the amount of heat history and the air pressure decrease speed of a tire having the same specifications as the requested tire.

The storage unit 32 stores information about the amount of thermal history and the rate of decrease in air pressure of the tire of each vehicle, which is transmitted from each air pressure management device 10 . Specifically, the storage unit 32 constitutes a database that stores information on the amount of heat history and the air pressure decrease rate for each tire specification. This database is updated periodically or in real time based on the acquired information on the amount of thermal history of the tire and the air pressure decrease rate.

Control unit 33 includes a CPU, a ROM, a RAM, and the like, and controls the overall operation of server device 30 based on information received from air pressure management device 10 or programs stored in storage unit 32 .

Next, the operation of the air pressure management device 10 according to this embodiment will be described. FIG. 3 is a flow chart showing the operation procedure of the air pressure management device. FIG. 4 is a diagram showing the relationship between the temperature detected in a predetermined period and the detection frequency. FIG. 5 is a diagram showing the relationship between the temperature acceleration factor and temperature. FIG. 6 is a schematic diagram of a threshold table showing the relationship between the amount of thermal history and the air pressure drop degree threshold. FIG. 7 is a diagram showing an estimated air pressure drop time until the air pressure reaches the limit air pressure.

The operation procedure from step ST1 to step ST10 shown in FIG. 3 is periodically repeated. As shown in FIG. 3 , first, the sensor receiving unit 11 acquires information on the temperature and air pressure of the tire 2 measured by the sensor 3 provided on each tire 2 of the vehicle 1 every predetermined time (for example, 10 minutes). receive) (step ST1). The acquired information is stored in the storage unit 12 as history information associated with the time information for each tire 2 identified by the sensor ID.

Next, the thermal history amount calculator 19 calculates the thermal history amount of the tire 2 for a predetermined period (step ST2). Here, the thermal history amount calculation unit 19 calculates the thermal history amounts of all the six tires 2, but one tire 2 will be explained for convenience of explanation. The thermal history calculation unit 19 classifies the temperature information of the tire 2 for a predetermined period (for example, the last month) acquired from the storage unit 12 into temperature intervals of 1°C between 0°C and 120°C. , to obtain the detection frequency of the measured value in each temperature interval, as shown in FIG. This detection frequency indicates the accumulated time when the temperature information measured during the predetermined period is classified into each temperature section. In general, the temperature of the tire 2 tends to be low on the outer rear wheels of the vehicle and high on the inner rear wheels. Therefore, it is preferable to acquire the detection frequency (cumulative time) according to the wheel position where the tire 2 is mounted.

The amount of thermal history for a predetermined period is obtained by dividing a temperature acceleration coefficient (acceleration coefficient) related to the state change of the tire member, which is given in advance using temperature as a parameter, and a plurality of temperature information measured during the predetermined period into predetermined temperature intervals. It is calculated by the following formula (1) using the actual detection frequency (cumulative time).

Thermal history amount for a predetermined period=Σ(K(ti)×T(ti)) (1)

In this formula (1), the amount of heat history for a predetermined period is the total sum of section heat amounts applied to all the above-described temperature sections. Also, ti is the temperature, and K(ti) is the temperature acceleration coefficient at the temperature ti. Also, T(ti) is the accumulated time at the temperature ti. Here, the temperature acceleration coefficient K(ti) is a contribution coefficient related to the state change of the tire member with the temperature ti as a parameter. It is considered that In FIG. 5, α is set to 0.069 based on the assumption that tire deterioration doubles when the temperature ti rises by 10°C. The temperature ti is the maximum temperature in each temperature section, but is not limited to this, and may be, for example, the average temperature in each temperature section. Accumulated time is the accumulated time in a temperature section including that temperature.

Next, the air pressure decrease speed threshold setting unit 20 sets an air pressure decrease speed threshold based on the calculated amount of thermal history (step ST3). In this embodiment, the air pressure decrease speed threshold setting unit 20 includes a threshold table 20a that defines air pressure decrease speed thresholds associated with thermal history amounts. Therefore, as shown in FIG. 6, the air pressure decrease speed threshold setting unit 20 refers to the threshold table 20a to set the air pressure decrease speed threshold Q corresponding to the calculated amount of heat history R. According to this configuration, it is possible to change the air pressure decrease speed threshold to be set according to the current amount of thermal history, so it is possible to accurately determine whether or not there is an abnormality in the air pressure of the tire 2 .

Next, the temperature-converted air pressure calculator 17 calculates the temperature-converted air pressure based on the acquired temperature and air pressure of each tire 2 (step ST4). Specifically, the temperature-converted air pressure calculator 17 converts the acquired air pressure of the tire 2 into air pressure at a specified temperature (for example, 25° C.) every predetermined time. According to this, fluctuations in the air pressure associated with changes in the temperature of the tire 2 are suppressed, and changes in the air pressure can be managed accurately.

Next, the air pressure decrease speed calculator 18 calculates the air pressure decrease speed from the calculated amount of change in the temperature-converted air pressure (step ST5). Specifically, by dividing the amount of change (kPa) in the temperature-converted air pressure before and after the elapse of a predetermined time by the predetermined time, it is possible to calculate the amount of air pressure decrease (kPa) per unit time (for example, one minute). can. In the present embodiment, attention is focused on the rate of decrease in air pressure, and the presence or absence of abnormal air pressure is determined based on the rate of decrease in air pressure.

Next, the first determination unit 22 determines whether or not the air pressure decrease speed calculated by the air pressure decrease speed calculation unit 18 is greater than the air pressure decrease speed threshold (step ST6). In this determination, if the air pressure decrease speed is equal to or less than the air pressure decrease speed threshold (step ST6; No), the first determination unit 22 displays on the display unit 14 that the air pressure of the tire 2 is normal (step ST7). do. After step ST7, the air pressure management device 10 once terminates the process, but periodically repeats the process from step ST1. Further, in the determination described above, if the air pressure decrease speed is greater than the air pressure decrease speed threshold (step ST6; Yes), the first determination unit 22 displays on the display unit 14 that the air pressure of the tire 2 is abnormal. (Step ST8). According to this configuration, it is determined whether or not the air pressure of the tire 2 is abnormal based on the air pressure decrease speed threshold and the air pressure decrease speed set corresponding to the current amount of thermal history. It is possible to accurately determine whether or not there is an abnormality in the pneumatic pressure of the air.

Next, when it is determined that the air pressure of the tire 2 is abnormal, the control unit 16 determines the amount of time until the air pressure of the tire 2 reaches the limit air pressure when the tire 2 is continuously used at the calculated air pressure decrease rate. The period is displayed on the display unit 14 (step ST9). Specifically, when it is determined that the air pressure of the tire 2 is abnormal, the control unit 16 determines that the tire 2 is abnormal when the tire 2 is continuously used at the air pressure decrease rate described above, as shown in FIG. The time (pneumatic pressure drop estimation time) from time ta to time tb at which the pneumatic pressure of the tire 2 drops to the limit pneumatic pressure is estimated. Then, the control unit 16 displays the estimated air pressure drop estimated time on the display unit 14 . Here, the limit air pressure is the air pressure at which the vehicle 1 cannot run, and is set to, for example, 70% or less of the "maximum air pressure" defined by JATMA. This limit air pressure may be the above-described temperature-converted air pressure standard or the absolute air pressure standard. Also, when estimating the time until the air pressure drops to the limit air pressure, temperature changes during use of the tire estimated from annual temperatures may be taken into consideration.

According to this configuration, since the time until the air pressure drops to the limit air pressure is displayed, the driver (user) can evacuate to a safe place or move to a maintenance service shop within that time. . In the present embodiment, the control unit 16 is configured to estimate the time until the air pressure drops to the limit air pressure (pneumatic pressure drop estimation time), but the distance that the vehicle 1 can move may be estimated based on this time. .

Next, the control unit 16 causes the route guidance unit 15 to search for a route from the current position of the vehicle 1 to the nearest maintenance service shop, and displays the searched maintenance service shop on the display unit 14 (step ST10). In this case, route guidance to the maintenance service shop may be performed. In addition, if the control unit 16 cannot find the nearest maintenance service shop that can be moved within the time until the air pressure drops to the limit air pressure, the control unit 16 may display the contact information (telephone number) of this maintenance service shop. good. According to this, the on-site service can be requested while the vehicle 1 is evacuated to a safe place. After step ST10, the air pressure management device 10 temporarily terminates the process, but periodically repeats the process from step ST1. The process from step ST1 described above is periodically repeated.

In the above-described embodiment, the first determination unit 22 determines whether or not the air pressure decrease speed calculated by the air pressure decrease speed calculation unit 18 is greater than the air pressure decrease speed threshold. Following the determination by the unit 22, the second determination unit 23 may determine whether or not there is an abnormality in the air pressure of the set of tires 2 paired in advance. According to this configuration, in order to determine whether there is an abnormality in the air pressure of the pair of tires 2 based on the deviation of the air pressure decrease rate of the paired pair of tires 2, for example, even in the initial stage of the occurrence of a problem Whether or not there is an abnormality in the air pressure of the tire 2 can be determined with high accuracy, and by combining the determination by the second determination section 23 with the determination by the first determination section 22, the presence or absence of an abnormality in the air pressure of the tire 2 can be accurately and quickly determined. be able to.

Next, the operation of updating the threshold value table 20a of the air pressure decrease speed threshold setting unit 20 will be described. FIG. 8 is a diagram for explaining the operation of generating a threshold table based on information on the amount of thermal history and the rate of air pressure decrease. The update of the threshold table 20a is preferably performed periodically, for example, at the timing when the engine of the vehicle 1 is operated. In the present embodiment, the table updating unit 21 acquires information 25a regarding the amount of heat history and the rate of decrease in air pressure of tires having the same specifications (model number and size) as the tires 2 of the own vehicle from the database of the server device 30 . As shown in FIG. 8, the table updating unit 21 creates an approximate expression 25 representing the relationship between the amount of heat history and the rate of decrease in air pressure from the acquired pieces of information 25a. This approximate expression is a linear expression in the example of FIG. Also, this approximation formula may be created using, for example, the method of least squares. Then, the table update unit 21 adds a predetermined margin α to the approximate expression 25 to generate and update the threshold table 20a showing the relationship between the thermal history amount and the air pressure decrease speed threshold. This predetermined margin α is a constant value added to the approximate expression 25 in the axial direction of the air pressure decrease speed.

According to this configuration, the threshold table 20a is updated based on the information about the amount of heat history and the rate of decrease in air pressure acquired from the database. By displaying the air pressure abnormality on the display unit 14, the driver can be notified early. In FIG. 8, the information 25a regarding the amount of thermal history and the rate of decrease in air pressure is obtained from the database of the server device 30 and the approximate expression 25 is created. and the air pressure decrease rate may be acquired, and the threshold table 20a may be updated based on the information regarding the amount of thermal history and the air pressure decrease rate.

In the present embodiment, the thermal history amount was exemplified as the predetermined physical quantity related to the tire, but the present invention is not limited to this, and the air pressure and temperature of the tire can also be used as the predetermined physical quantity related to the tire. FIG. 9 is a schematic diagram of a threshold table showing the relationship between air pressure and air pressure drop threshold. In this configuration, as shown in FIG. 9, a threshold table is provided for each type of gas (air, nitrogen) enclosed in the tire 2 . Therefore, the threshold table to be used can be changed according to the enclosed gas, and the presence or absence of an abnormality in the air pressure of the tire 2 can be accurately determined. FIG. 9 shows a threshold table 20b1 showing the relationship between the air pressure of normal composition air and the air pressure drop threshold, and a threshold table 20b2 showing the relationship between the air pressure of nitrogen and the air pressure drop threshold. It is not limited and may contain other gases.

These threshold tables 20b1 and 20b2 define air pressure reduction speed thresholds associated with respective air pressures. In this case, an instantaneous value may be used for the air pressure, but it is preferable to use an average value of air pressure measured over a predetermined period (for example, one day or longer).

In this configuration, by referring to the threshold tables 20b1 and 20b2, it is possible to change the set air pressure decrease speed threshold according to the average air pressure in a predetermined period. Judgment can be made.

Further, although not shown, a configuration may be provided with a threshold table showing the relationship between the tire temperature as a physical quantity and the pneumatic pressure drop degree threshold. Also for the temperature in this case, an instantaneous value may be used, but it is preferable to use an average value of tire temperatures measured over a predetermined period (for example, one day or longer). In this configuration, by referring to a threshold table (not shown), it is possible to change the set air pressure decrease speed threshold according to the measured temperature. Judgment can be made.

As described above, the air pressure management device 10 according to the present embodiment includes the temperature-converted air pressure calculator 17 that calculates the temperature-converted air pressure of the tire 2 based on the acquired temperature and air pressure of the tire 2, and An air pressure drop rate calculation unit 18 for calculating an air pressure drop rate indicating the drop tendency of the air pressure of the tire 2 from the amount of change in the temperature-converted air pressure, and a threshold table defining the air pressure drop rate threshold associated with the amount of heat history related to the tire 2. 20a, the air pressure decrease speed threshold setting unit 20 that sets the air pressure decrease speed threshold corresponding to the acquired thermal history amount, and the tire 2 based on the calculated air pressure decrease speed and the set air pressure decrease speed threshold. Since the first determination unit 22 determines whether the air pressure is abnormal, the first determination unit 22 determines the air pressure decrease speed threshold and the air pressure decrease speed set corresponding to the current amount of thermal history. Based on this, it is possible to accurately determine whether or not the air pressure of the tire 2 is abnormal by determining whether or not the air pressure of the tire 2 is abnormal.

Further, according to the present embodiment, since any one of the thermal history amount, the temperature, and the air pressure of the tire 2 is used as the physical quantity, it is possible to accurately determine whether or not the air pressure of the tire 2 is abnormal.

Further, according to the present embodiment, the air pressure decrease speed calculation unit 18 calculates the air pressure decrease speed of the paired pair of tires 2 based on the wheel positions of the vehicle on which the tires 2 are mounted, and calculates each air pressure decrease speed. Since the second determination unit 23 is provided to determine whether or not the air pressure of one tire 2 out of the set of tires 2 is abnormal based on the deviation of the speed, for example, even in the initial stage of the occurrence of a problem, it can be accurately detected. Whether or not there is an abnormality in the air pressure of the tire 2 can be determined. Therefore, by combining the determination by the second determination unit 23 with the determination by the first determination unit 22, it is possible to accurately and quickly determine whether the air pressure of the tire 2 is abnormal.

Further, according to the present embodiment, the table updating unit 21 is provided for acquiring the thermal history amount and the air pressure decreasing rate of the tire 2 and updating the threshold table 20a based on the acquired thermal history amount and air pressure decreasing rate. , the threshold table 20a can be updated to the latest one at any time, so that the presence or absence of an abnormality in the air pressure of the tire 2 can be accurately determined.

Further, according to the present embodiment, the table updating unit 21 acquires the amount of heat history and the air pressure decrease rate of the tire 2 having the same specifications as the tire 2 accumulated in the database of the server device 30, so that a large amount of data is obtained. It can be utilized, and whether or not there is an abnormality in the pneumatic pressure of the tire 2 can be determined with high accuracy.

Further, according to the present embodiment, when the first determination unit 22 determines that the air pressure of the tire 2 is abnormal, when the tire 2 is continuously used at the calculated air pressure decrease rate, the air pressure of the tire reaches the limit. Since the display unit 14 displays the time until the air pressure drops, the driver (user) can evacuate to a safe place or move to a maintenance service shop within that time.

The air pressure management method according to the present embodiment includes step ST4 of calculating the temperature-converted air pressure of the tire based on the obtained temperature and air pressure of the tire 2, and calculating the air pressure decrease speed from the amount of change in the temperature-converted air pressure in a predetermined period. Using step ST5 and the threshold table 20a that defines the air pressure decrease speed threshold value associated with the thermal history amount of the tire 2, step ST3 of setting the air pressure decrease speed threshold value corresponding to the acquired thermal history amount, and a step ST6 of determining whether or not the air pressure of the tire 2 is abnormal based on the pneumatic pressure lowering speed and the set pneumatic pressure lowering speed threshold. Therefore, it is possible to accurately determine whether or not there is an abnormality in the air pressure of the tire 2 .

The air pressure management program according to the present embodiment calculates step ST4 for calculating the temperature-converted air pressure of the tire based on the obtained temperature and air pressure of the tire 2, and calculates the air pressure decrease speed from the amount of change in the temperature-converted air pressure in a predetermined period. Using step ST5 and the threshold table 20a that defines the air pressure decrease speed threshold value associated with the thermal history amount of the tire 2, step ST3 of setting the air pressure decrease speed threshold value corresponding to the acquired thermal history amount, and The air pressure management device 10 is caused to execute step ST6 of determining whether or not the air pressure of the tire 2 is abnormal based on the air pressure lowering speed and the set air pressure lowering speed threshold. Therefore, it is possible to accurately determine whether or not there is an abnormality in the air pressure of the tire 2 .

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments.

REFERENCE SIGNS LIST 1 vehicle 2 tire 3 sensor 3a air pressure sensor 3b temperature sensor 4 outside air temperature sensor 10 air pressure control device 12 storage unit 14 display unit (notification unit)
16 Control Unit 17 Temperature-Converted Air Pressure Calculator 18 Air Pressure Decrease Speed Calculator 19 Thermal History Amount Calculator (Physical Quantity Acquisition Unit)
20 air pressure decrease speed threshold setting unit 20a, 20b1, 20b2 threshold table 21 table update unit 22 first determination unit 23 second determination unit 30 server device (external device)
32 storage unit

Claims (7)

a temperature-converted air pressure calculator that calculates the temperature-converted air pressure of the tire based on the obtained tire temperature and air pressure;
an air pressure decrease speed calculation unit that calculates an air pressure decrease speed indicating a decreasing tendency of the air pressure of the tire from the amount of change in the temperature-converted air pressure in a predetermined period;
a heat history amount calculation unit that calculates a heat history amount, which is an index indicating the amount of heat received by the tire in a predetermined period, based on the acquired temperature of the tire;
an air pressure decrease speed threshold setting unit that sets the air pressure decrease speed threshold value corresponding to the calculated thermal history amount using a threshold table that defines the air pressure decrease speed threshold value associated with the thermal history amount of the tire;
a first determination unit that determines whether the air pressure of the tire is abnormal based on the calculated air pressure decrease speed and the set air pressure decrease speed threshold;
An air pressure management device comprising: The air pressure decrease speed calculation unit calculates the air pressure decrease speed of the paired pair of tires based on the wheel positions of the vehicle on which the tires are mounted,
2. The air pressure management device according to claim 1 , further comprising a second determination unit that determines whether or not the air pressure of one of the pair of tires is abnormal based on the deviation of each air pressure decrease rate. 3. The tire according to claim 1 , further comprising a table updating unit that acquires the thermal history amount and the air pressure decrease rate of the tire and updates the threshold table based on the acquired thermal history amount and the air pressure decrease rate. air pressure management device. 4. The air pressure management device according to claim 3 , wherein the table updating unit acquires the thermal history amount and the air pressure decrease rate of a tire having the same specifications as the tire stored in an external device. When the first determination unit determines that the air pressure of the tire is abnormal,
5. The method according to any one of claims 1 to 4 , further comprising a notification unit that notifies the time until the air pressure of the tire decreases to the limit air pressure when the tire is continuously used at the calculated air pressure decrease rate. air pressure management device. calculating a temperature-converted pneumatic pressure of the tire based on the obtained tire temperature and pneumatic pressure;
calculating an air pressure decrease rate from the amount of change in the temperature-converted air pressure in a predetermined period;
a step of calculating a thermal history amount, which is an index indicating the amount of heat received by the tire during a predetermined period, based on the acquired temperature of the tire;
setting the air pressure decrease speed threshold value corresponding to the calculated thermal history amount using a threshold table that defines the air pressure decrease speed threshold value associated with the thermal history amount of the tire;
a step of determining whether the air pressure of the tire is abnormal based on the calculated air pressure decrease speed and the set air pressure decrease speed threshold;
air pressure management method. calculating a temperature-converted pneumatic pressure of the tire based on the obtained tire temperature and pneumatic pressure;
calculating an air pressure decrease rate from the amount of change in the temperature-converted air pressure in a predetermined period;
a step of calculating a thermal history amount, which is an index indicating the amount of heat received by the tire during a predetermined period, based on the acquired temperature of the tire;
setting the air pressure decrease speed threshold value corresponding to the calculated thermal history amount using a threshold table that defines the air pressure decrease speed threshold value associated with the thermal history amount of the tire;
a step of determining whether the air pressure of the tire is abnormal based on the calculated air pressure decrease speed and the set air pressure decrease speed threshold;
air pressure management program that causes the air pressure management device to execute

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